The invention relates to geodesic dome structures, and more particularly to components of and methods of construction thereof, especially to strut end connectors and methods of assembly and to pre-finished panels and means of attachment thereof to the struts, and to space frames.
Residential geodesic dome structures formed by combining triangular panels into three-dimensional forms, often twenty-sided icosahedrons, have received rather good public acceptance. Nevertheless, for quite a number of reasons, very few conventional builders or skilled individual do-it-yourselfers are able to efficiently construct residential geodesic dome structures.
Several of my prior U.S. patents disclose so-called three-frequency penthex dome shell kits. The structures therefrom include triangular panels which are partially prefabricated of wood 2 by 4's. The outer edge beams of the triangles are inclined at predetermined angles and have alignable predrilled bolt holes therein. The partially constructed triangular panels then are positioned to align the bolt holes in adjacent triangular panels and are systematically bolted together to form a shell which has the shape of an icosahedron. The physical handling and alignment of such partially constructed triangular panels is difficult, especially as the height of the dome under construction increases. The problem is amplified as the size of the dome to be constructed increases and the size of the preconstructed panels increases. Furthermore, after the dome shell has been constructed, it is necessary to staple insulation between the various strut members of which the triangles are formed, and finally, to attach triangular ceiling panels thereto, and finally to provide suitable paint or other finish material thereto. Especially at the higher interior elevations of the dome, and especially for larger domes, the difficulty of the interior construction and finish work that must be performed after the basic shell structure has been completed greatly increases the total cost of the completed dome structure. Furthermore, there has been great difficulty in achieving uniform, gap-free interior joints between adjacent triangular panels or sections for prior geodesic domes. Obviously, such gaps detract from the appearance of the interior of a dome.
Various other approaches to assembly of residential geodesic dome structures and components therefor have been proposed, such as the dome kits sold by Monterey Domes of Riverside, Calif., and those disclosed in U.S. Pat. Nos. 4,262,461; 3,530,621; 4,295,303; 3,918,233 and 4,005,561, which are listed in order of believed relevance to the present invention. Some of these references disclose various kinds of elements for interconnecting ends of struts to allow constructing of a dome skeleton to which outer panels, insulation, and inner panels are subsequently attached. But none of the prior systems overcome the above-mentioned shortcomings of difficulty of assembly and interior finishing operations that are required to complete the dome structure. Most of the prior devices also result in waste of an undue amount of material, and some suffer from significant structural weaknesses that eventually result in undesirable cracking of interior wall surfaces.
In view of the numerous very attractive residential dome designs that are available and have been constructed, and in view of some important advantages that should be present in a geodesic dome structure, including high structural strength, reduced amount of material required to provide a predetermined amount of floor space, and increased energy efficiency, it is clear that the difficulty and high labor cost of assembly of known geodesic dome structures has prevented as widespread use of residential geodesic dome structures as would otherwise be the case. Thus, there is clearly an unmet need for an improved geodesic dome structure and method of construction thereof that reduces the amount of material and labor that is required to assemble geodesic domes.
A vast majority of residential geodesic dome structures that have been completed to date have diameters in the range from 39 to 45 feet. Very few geodesic domes having diameters as large as 90 feet have ever been constructed, due to the fact that the above mentioned difficulties of assembly are amplified as the size of the dome increases. Nevertheless, the inherent advantages of the geodesic dome structure should apply equally as well to large geodesic domes as to smaller ones.
Accordingly, it is an object of the invention to provide a geodesic dome structure that is more easily assembled than those of the prior art and therefore can be less expensively assembled.
It is another object of the invention to provide a geodesic dome structure and method of assembly that can be accomplished by a small work crew.
It is another object of the invention to provide a geodesic dome structure and method of assembly that results in increased structural strength, including increased resistance to both small compressive hub deformations and small tensile hub deformations.
It is another object of the invention to provide an improved geodesic dome structure and method of assembly that eliminates or greatly decreases labor required to finish the interior of the structure once the shell has been completed.
It is another object of the invention to provide an improved geodesic dome structure and method of making that makes it more practical to construct geodesic domes that are substantially larger than 45 feet in diameter.
It is another object of the invention to provide an improved strut end connector system which is compatible with the design and assembly of a wide variety of geodesic dome geometrical structures.
It is another object of the invention to minimize the size of the panels that are required to construct a very large geodesic dome.
Sub-structures known as "space frames" in the past have been used in construction of various building structures and in other structures. Space frames typically include an upper rectangular grid and a lower rectangular grid, each composed of grid struts which are connected together at the appropriate hubs. The upper grid and the lower grid are interconnected and held in spaced parallel relationship to each other by "inter-grid struts", which are also connected to appropriate hubs to rigidly maintain the parallel relationship of the upper and lower grids. Up to now, construction of such space frames has been expensive and difficult. "Vaulted" space frame structures in which some or all of the struts of the lower grid are shorter than struts of the upper grid are known.
Accordingly, it is another object of the invention to provide a strut end connection system which facilitates inexpensive and convenient construction of flat and/or vaulted space frames.